JPH08150465A - Preparation of nozzle for injection molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a nozzle for injection molding executing brazing sealing a space surrounding a heating wire and the casting of a thermally conductive material into the sealed space in a single cycle of a vacuum furnace. SOLUTION: A heating wire is mounted in a space 42 formed between an inner core 12, an outer collar and an outer sleeve 38. The space 42 is first sealed by brazing with a nickel alloy brazing material, and then, a copper conductive material 50 is cast into the space 42. Both the brazing and casting are done in a single cycle of a vacuum furnace. An insulative cap 54 is placed over the nozzle assembly 46 so as to cool the thermally conductive material melted by an inert gas fed to the vacuum furnace from the bottom in due order. This produces unidirectional solidification to avoid the formation of voids in the thermally conductive material, so that the thermal conductivity of the nozzle can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding apparatus, and more particularly to a method for manufacturing an injection molding nozzle having a heating wire for both brazing and casting in one heating operation of a vacuum furnace.

[0002]

2. Description of the Related Art Providing an integral heating wire in an injection molding nozzle has great advantages in terms of improving its heat conduction performance, suppressing corrosion, and extending its life. During the manufacture of such injection molding nozzles, it is known to first seal the components by brazing using a vacuum furnace to form a space surrounding the spiral of the heating wire. After this, the nozzle is again loaded into the vacuum furnace and heated in order to cast a heat conductive material such as copper into the sealed space surrounding the spiral portion of the heating wire. In this method, a thermally conductive material such as beryllium-copper alloy may be selected, which has a lower melting point than brazing materials such as nickel alloys.

An example of application of this method is described in Applicant's US Pat. Nos. 4,355,460, 4,403,405 and 4,771,164.

[0004]

Although these conventional methods have many advantages, the sealing of the space surrounding the spiral of the heating wire and the casting of copper into this sealed space are performed separately. However, the heating operation of the vacuum furnace needs to be performed twice at different temperatures.

Further, it has been confirmed that the conventional method of casting the heating wire in the heat conductive material is effective in reducing the air pockets generated in the nozzle and improving the heat transfer performance. Recently, it has been found that the thermal conductivity of this nozzle can be further improved by changing the cooling method of the nozzle. This is a method of unidirectionally solidifying the thermally conductive material from the bottom to the top to prevent void formation during shrinkage of the cast material.

Therefore, an object of the present invention is to provide an injection molding nozzle for performing both brazing for sealing a space surrounding a heating wire and casting of a heat conductive material into the sealed space in one operation of a vacuum furnace. It is to provide a manufacturing method of.

Another object of the present invention is to provide a cooling method for a nozzle, which is manufactured by solidifying a heat conductive material in one direction from the bottom in a space.

[0008]

SUMMARY OF THE INVENTION The present invention includes a rear end, a front end, an inner body having a molten material passage formed therethrough from the rear end, and the interior adjacent to the rear end. An external collar portion provided on the main body portion, an external sleeve portion provided from the external collar portion toward the front end portion, and a radial portion that penetrates the turning portion and the external collar portion when wound around the internal main body portion. Of a heating wire having a lead portion and a heat conducting portion formed between the inner body portion and the outer sleeve portion so as to surround the spiral portion of the heating wire. A method, wherein an outer collar and the heating wire are attached to an inner body to form an assembly, and an outer sleeve is formed between the inner body and the inner collar to form a space surrounding the spiral portion of the heating wire. Attach the inner body, the outer When each junction between collar and said external sleeve a brazing material is applied, respectively, assume an upright position in which said assembly is placed the front part upwards,
The assembly is brazed under a substantially oxygen-free atmosphere in a vacuum furnace to seal the space, and further integrated with the inner body portion, the outer collar portion, the heating wire and the outer sleeve portion. A thermally conductive material is cast into the space while maintaining the upright position of the assembly in a substantially oxygen-free atmosphere in a vacuum furnace to form the combined heat conducting portion to achieve the desired shape and finish. Wherein the nozzle that has been cast to be machined is provided with the thermally conductive material having a melting point higher than that of the brazing material, and the assembly in one operation of the vacuum furnace. Are brazed together, and the thermally conductive material is cast into the space, then initially above the melting point of the brazing material and above the melting point of the thermally conductive material. Sufficient time to raise the vacuum furnace temperature to a first temperature, then lower the vacuum furnace temperature to a second temperature below the freezing point of the brazing material, and to braze the assembly. The space surrounding the spiral of the heating wire between the outer sleeve and the inner body between the outer sleeve and the inner body without holding the brazing material and melting the brazing material. It is characterized in that the vacuum furnace temperature is raised to a third temperature higher than the melting point of the heat conductive material so as to be cast into.

[0009]

1 and 2 show the component parts of an injection molding nozzle provided with a heating wire assembled by the method of the present invention. A heating wire 10 is provided along an inner body 12 made of a material such as hot work tool steel.

The inner main body 12 of the present embodiment has a head 14 on the upper end 16 side, in which a plurality of grooves 18 for vertically flowing a molten heat conductive material are engraved as described later. The heating wire 10 is wound around the inner body 12, and the spiral part 20 is provided.
It is composed of two lead portions 22 provided so as to protrude in the radial direction near the lower end 24 of the inner body 12.

The heating wire 10 maintains a predetermined coil shape so that the heating wire 10 is wound less in the intermediate region of the inner body 12 than in other places. The heating wire 10 of the present embodiment is made by drawing a resistance wire through an electrically insulating material such as magnesium oxide packed in a steel casing. Depending on the application, different types and shapes of heating wire can be used depending on the thermal requirements.

On the other hand, a hollow outer collar 26 having an opening 28 is attached to the lower end 24 side of the inner body 12. Here, the two lead portions 22 of the heating wire 10 are connected to the external collar 26.
Through a radially oriented opening 28 in the. The plug 30 has two holes 32 through which the lead portion 22 passes.
And the plug 30 is attached to the opening 2 of the outer collar 26.
8 is assembled, the lead portion 22 is pulled out through the hole 32.

The outer collar 26 of this embodiment has an insulating flange 34 for supporting the nozzle 36 so as not to cause excessive heat loss when the nozzle 36 is mounted on a mold (not shown) to be cooled. Have.

Further, the outer sleeve 38 made of a protective material such as stainless steel is a spiral portion 2 of the heating wire 10.
It is mounted around 0 with a space 42 between it and the inner body 12. Here, the lower end 40 of the outer sleeve 38 is brought into contact with and assembled to the seat portion of the outer collar 26.

As shown in FIG. 2, the outer sleeve 38 of the present embodiment is located above the head 14 of the inner body 12 and is located above the hopper 4.
4 extends upwardly beyond the upper end 16 of the inner body 12 to form 4. During the assembly process, the inner body 12, outer collar 26, plug 30, and outer sleeve 38 are laser welded in place to form the assembly 46.

Thereafter, the inner body 12, the heating wire 10, the plug 30, and the outer sleeve 3 shown by the reference numeral 48 in FIG.
A brazing material such as a nickel alloy is applied to each of the joints of No. 8. Beads are formed for the outer joint and powder is used for the inner joint. In addition, spheres of thermally conductive material are packed into the hopper 44 through the upper openings 52.

The heat conductive material 50 of the present embodiment is pure copper and has a melting point of about 1082.22 ° C. (1980 ° F.) higher than that of a nickel alloy having a melting point of about 1010 ° C. (1850 ° F.). Other combinations of materials can be used as long as the thermally conductive material 50 has a melting point higher than that of the braze material and the braze sealed location will not remelt due to casting.

After the heat conductive material 50 is packed in the hopper 44, the assembly 46 is fitted with the insulating cap 54. As shown in FIG. 2, the insulating cap 54 is used in this embodiment.
Has a tapered central opening 56 with an inlet 58 through which the assembly 46 passes. The central opening 56 has a tapered portion 60 which is tapered toward a vent port 62 extending to the upper end 64 of the insulating cap 54.

The insulating cap 54 is removably held at a position where the tapered portion 60 is placed on the upper end 66 of the outer sleeve 38.

As shown in FIG. 2, the skirt 68 of the insulating cap 54 surrounds the insulating flange 34 of the outer collar 26, but the lower portion 69 of the assembly 46 is not covered by the insulating cap 54. In other embodiments, more or less, or even complete coverage of the assembly may be provided with an insulating cap 54 if needed to unidirectionally solidify the thermally conductive material 50.

Preferably, the insulating cap 54 is made of a suitable ceramic material, although other suitable materials such as, for example, stainless steel can be used.

As shown in FIG. 3, the assembly 46 is placed on the rack 70 while keeping the upright position, and is loaded into the vacuum furnace 72 for heating in batch. In this embodiment, the insulating cap 54 is shown as being separated and attached to each assembly 46, but a separately prepared common insulating cap may be attached to the assembly for batch processing.

During one operation of the vacuum furnace 72, the assembly 46 encloses the heating wire 10 in the space 4 as described below.
It is brazed to seal the two and then a thermally conductive material is cast into the space 42 to form the nozzle 36.

The vacuum furnace 72 is gradually heated to extract oxygen therein to maintain the inside of the furnace at a high vacuum. At this time, the vent 62 of the insulating cap 54 extracts oxygen trapped inside the insulating cap 54. The vacuum furnace 72 is then partially replaced with an inert gas such as argon or nitrogen to avoid sputtering. The vacuum furnace 72 has a first temperature of about 1065.5 which is higher than the melting point of the nickel alloy and lower than the melting point of the copper heat conductive material 50.
Heat to 6 ° C (1950 ° F).

At this time, the nickel alloy applied along the joints 48 between the heating wire 10, the inner body 12, the plug 30, and the outer sleeve 38 melts. After that, the temperature of the vacuum furnace 72 is set to a second temperature lower than the solidification temperature of the nickel alloy.
The temperature of about 982.22 ° C. (1800 ° F.).

The second temperature is the spiral portion 20 of the heating wire 10.
It is held for about 30 minutes to seal the space 42 surrounding it and at the same time braze the assembly 46 together. This results in a diffused braze layer in the joint steel having a higher melting point than that of the copper thermally conductive material 50. After this, the temperature of the vacuum furnace 72 is set to a third temperature of about 1112.78 ° C (2035 ° F), which is not high enough to melt the diffusion brazing layer at the joint and is sufficiently higher than the melting point of the heat conductive material 50. To raise.

When the copper heat conductive material 50 is melted, the melted copper flows from the hopper 44 through the groove 18 in the head 14 of the inner body 12 into the space 42 surrounding the spiral portion 20 of the heating wire 10. Meet As described above, the melting point of the brazing layer along the joint is sufficiently higher than the melting point before brazing, so that the molten copper does not leak through the brazed joint in the space 42. The heating wire 10 can be cast by filling the entire area.

After that, the operation of the vacuum furnace 72 is completed by gradually lowering the temperature of the vacuum furnace 72 while supplying an inert gas such as nitrogen before taking out the cast nozzle 36.

By covering with the insulating cap 44, the copper heat conductive material 50 cools from the bottom, so that the heat conductive material 50 solidifies in one direction from the bottom to the top. This method will prevent the formation of voids from shrinkage of the thermally conductive material 50 during cooling. Therefore, the heat from the heating wire 10 can be uniformly transferred to the molten material flowing through the nozzle 36.

The heat conductive material 50 can be metallurgically bonded to the steel casing of the heating wire 10 as well as the steel inner body 12, the outer collar 26 and the outer sleeve 38 by casting in a vacuum atmosphere. . Furthermore, it becomes possible to obtain an injection molding nozzle having a significantly improved thermal characteristic in combination with the unidirectional solidification of the heat conductive material.

After taking out from the vacuum furnace 72, the hopper 44
The upper portion 74 of the outer sleeve 38 forming the is removed by machining and further finished.

Further, as shown in FIG. 6, the nozzle has a central hole 76 formed in the central portion from the rear end portion 78 to the front end portion 80, and further has a groove 84 in the rear end portion 78 and extends forward from this groove 84. Hole processing is performed to form the thermocouple holes 82.
Further, the screw hole 86 for attaching the nozzle is formed in the rear end portion 78.
(See FIG. 4).

In this embodiment, the seat portion 88 for mounting the gate insert is formed on the front end portion 80 of the nozzle 36 by machining, but this can be processed into various other gate shapes.

As shown in FIG. 6, the completed nozzle 36 is shown.
Has an inner body 90 through which a central hole 76 extends. The heat conducting portion 92 formed of the copper heat conducting material 50 is integrally connected to the inner body portion 90 as well as the heating wire 10, the outer collar portion 94 having the plug 30, and the outer sleeve 96. In addition, the heat conductive material 50 is applied to the head 14 of the inner body 12.
Completely fills the groove 18 surrounding the
The thermal conductivity in the vicinity can be improved.

In use, the nozzle 36 is mounted in a cooled mold and molten material is directed through a central hole 76 to a gate leading to the cavity. The method of using the injection molding nozzle is the same as the conventional method, but the heat transfer performance of the nozzle manufactured by the method of the present invention is significantly improved.

Another embodiment of the present invention will be described with reference to FIG.

Most of the elements are the same as those in the above-described embodiment, and the same reference numerals are given to them. In this embodiment, the insulating cap 98 has a hollow body 100 and a lid 102 having a vent 104. The body portion 100 is placed at the upper end 66 of the outer sleeve 38 and is placed in contact with the lower end portion 1 thereof.
Has 06.

In this embodiment, instead of forming the hopper 44 on the outer sleeve 38, the insulating cap 98 is formed with the hopper 108 for filling the small balls of the heat conductive material 50.
The small spheres of the heat conductive material 50 are packed above the ribs 110 so that air can be vented while keeping the space 112 below.

On the other hand, the manufacturing method of this embodiment is the same as that of the above embodiment except that there is no upper portion 74 of the outer sleeve 38 which is removed after the casting is completed.

The insulating cap 98 is simply removed and the nozzle 36 is given the necessary finishing. Preferably, the insulating cap 98 is made of a ceramic material and is sprayed on its inner surface with an anti-adhesion agent that prevents large amounts of molten copper from depositing for reuse.

[0041]

As described above, according to the present invention, the brazing for sealing the space surrounding the heating wire in one operation of the vacuum furnace and the casting of the heat conductive material into the sealed space are both performed. Therefore, it is possible to manufacture the nozzle more efficiently and at a lower cost as compared with the case where the vacuum furnace is operated each time to perform brazing and casting.

[Brief description of drawings]

FIG. 1 is an exploded view showing main elements of an injection molding nozzle according to the present invention.

FIG. 2 is a sectional view showing an assembly of an injection molding nozzle according to the present invention.

FIG. 3 is a perspective view showing a state in which the assembly is collectively loaded into a vacuum furnace.

FIG. 4 is a plan view of the completed injection molding nozzle seen from the rear end side.

FIG. 5 is a plan view of the completed injection molding nozzle seen from the front end side.

6 is a sectional view taken along line VI-VI of FIGS. 4 and 5. FIG.

FIG. 7 is a sectional view showing another embodiment of the present invention.

[Explanation of symbols]

 10 Heating Wire 12 Internal Body 26 External Collar 30 Plug 36 Nozzle 38 External Sleeve 42 Space 50 Thermal Conductive Material 54, 98 Insulation Cap 72 Vacuum Furnace

Claims (10)

[Claims] 1. A rear end portion, a front end portion, an inner main body portion having a molten material passage formed through the interior from the rear end portion, and an outer portion provided on the inner main body portion adjacent to the rear end portion. An electrode having a collar portion, an outer sleeve portion provided from the outer collar portion toward the front end portion, a turning portion when wound around the inner main body portion, and a lead portion protruding radially through the outer collar portion. A method for manufacturing an injection molding nozzle, comprising: a heat wire; and a heat conducting portion formed between the inner body portion and the outer sleeve portion so as to surround the spiral portion of the heating wire. And the heating wire are mounted on an inner body to form an assembly, and an outer sleeve is mounted so as to form a space surrounding the spiral portion of the heating wire between the inner body and the inner body. , The external collar and the external sleeve Brazing material is applied to each joint between the tubes, and when the assembly is in an upright position with the front end facing up, a substantially oxygen-free atmosphere in a vacuum furnace is provided to seal the space. Initially, the assembly is brazed, and substantially oxygen in the vacuum furnace is formed so as to form the heat conducting portion integrally combined with the inner body portion, the outer collar portion, the heating wire and the outer sleeve portion. A heat-conductive material is cast into the space while maintaining the upright position of the assembly in an atmosphere free of air, and the nozzle is machined to provide the desired shape and finish. In, the thermally conductive material has a melting point higher than that of the brazing material, brazing the assembly together in a single operation of the vacuum furnace, and Casting material into the space, then increasing the vacuum furnace temperature to a first temperature that is first above the melting point of the brazing material and below the melting point of the thermally conductive material, and then the brazing material. The vacuum furnace temperature is reduced to a second temperature below the freezing point of the brazing material and held at the second temperature for a time sufficient to braze the assembly, after which the brazing material is melted. A temperature higher than the melting point of the heat conductive material so as to cast the heat conductive material into the space surrounding the spiral portion of the heating wire between the outer sleeve and the inner body without
The method for producing an injection molding nozzle, wherein the temperature of the vacuum furnace is raised to the temperature of 1. 2. The injection according to claim 1, wherein in the operation of the vacuum furnace, the vacuum furnace is gradually cooled while supplying an inert gas before taking out the cast nozzle. Manufacturing method of molding nozzle. 3. During the heating operation of the vacuum furnace, the assembly is covered with an insulating cap having an opening with an inlet at the bottom, whereby the thermally conductive material is cooled upwards in a stepwise manner. The method for manufacturing an injection molding nozzle according to claim 2. 4. The method for manufacturing an injection molding nozzle according to claim 3, wherein a predetermined portion of the assembly is inserted upward into the opening of the insulating cap. 5. The upper end of the outer sleeve extends upwardly in an upright position beyond the front end to form a hopper, which is defined within the hopper prior to loading the assembly into the vacuum furnace. An amount of the thermally conductive material such that the thermally conductive material melts during casting in the vacuum furnace and further the helix of the heating wire between the outer sleeve and the inner body. The method of manufacturing an injection molding nozzle according to claim 4, wherein the nozzle is made to flow into the space surrounding the nozzle. 6. The injection according to claim 5, wherein the insulating cap is detachably retained so that a part of the assembly is abutted with the upper end of the outer sleeve and is accommodated in the opening. Manufacturing method of molding nozzle. 7. The method of manufacturing an injection molding nozzle according to claim 6, wherein the insulating cap includes a vent port extending upward from the opening for housing the assembly. 8. The method of manufacturing an injection molding nozzle according to claim 7, wherein the inner body, the outer collar, and the outer sleeve are temporarily attached together by welding before brazing. 9. The method for manufacturing an injection molding nozzle according to claim 8, wherein the heat conductive material is made of copper. 10. The method for manufacturing an injection molding nozzle according to claim 9, wherein the brazing material is a nickel alloy.